1. Field of the Invention
The present invention generally relates to cable connectors. More specifically, the present invention relates to a balanced transmission cable connector where first signal contacts, second signal contacts and ground contacts are arranged in an insulative block body. Here, the first signal contacts and the second signal contacts face each other in a line (vertical) direction. The first signal contacts/the second signal contacts and the ground contacts are alternately arranged in a row direction. The first signal contact, the second signal contacts and the ground contacts are connected to first signal wires, second signal wires and drain wires, respectively, of ends of the balanced transmission cable.
2. Description of the Related Art
As ways for transmitting data, there are a normal transmission type and a balanced transmission type. In the normal transmission type, a single electric wire is used for every data stream. In the balanced transmission type, two electric wires which form a couple for every data stream are used so that a positive signal and a negative signal having the same size as that of the positive signal but having a different direction from that of the positive signal are simultaneously transmitted. The balanced transmission type, compared to the normal transmission type, has an advantage in that there may not be noise influence. Accordingly, the balanced transmission type has been widely used in fields where signals are transmitted at a high speed.
In the meantime, FIG. 1 is a perspective view schematically illustrating a related art balanced transmission cable connector. FIG. 2 is an exploded perspective view of the balanced transmission cable connector illustrated in FIG. 1. FIG. 3 is a cross-sectional view of a balanced transmission cable 20. FIG. 4 is a view illustrating a connection part of an end of the balanced transmission cable 20 and a contact assembly body 51. FIG. 4(A) is a perspective view and FIG. 4(B) is a cross-sectional view taken along a line A-A.
In FIG. 1 through FIG. 4, “X1-X2” indicates a width direction, “Y1-Y2” indicates a longitudinal direction, and “Z1-Z2” indicates a height direction, of the balanced transmission cable connector.
The balanced transmission cable includes, as illustrated in FIG. 1 and FIG. 2, the balanced transmission cable 20, the connector assembly body 51, a pair of lock arms 56 and 57, a spacer 60, a shield cover assembly body 80, a hood 100, an outer cover 110, and an inner cap 400. See, for example, Japanese Laid Open Patent Application Publication No. 2007-12588.
The balanced transmission cable 20 includes, as illustrated in FIG. 3, plural pair electric wires 21. Plural pair electric wires 21 are provided inside a tube having a double covering structure formed of an external covering 27 and a shield mesh line 28. Insulative covering signal electric wires 22-1 and 22-2 forming a pair for balanced signal transmission and the drain wire 25 are bundled by a metal tape winding around the insulative covering signal electric wires 22-1 and 22-2 and the drain wire 25 in a spiral manner, so that each of the pair electric wires 21 is shielded. The insulative covering signal electric wires 22-1 and 22-2 and the drain wire 25 extend outside from an end of each of the pair electric wires 21. Head ends of the insulative covering signal electric wires 22-1 and 22-2 are processed so that a first signal wire 23-1 and a second signal wire 23-2 are exposed.
As illustrated in FIG. 4, in an insulative block body 52 of the contact assembly body 51, a first signal contact 53, a second signal contact 54 and a ground contact 55 are alternately arranged in a row direction (X1-X2 direction). The first signal contact 53 and the second signal contact 54 face each other in a line direction (Z1-Z2 direction). In addition, Y1 side ends of the lock arms 56 and 57 are provided one at each end in the X1-X2 direction of the block body 52.
The first signal contact 53 and the second signal contact 54 include a first signal wire connecting part 53c and a second signal wire connecting part 54c, respectively. The first signal wire connecting part 53c and the second signal wire connecting part 54c project to a rear surface side (Y2 side) of the block body 52. The first signal wire connecting part 53c and the second signal wire connecting part 54c have L-shaped cross-sectional configurations.
The ground contact 55 includes a plate-shaped part 55c and a drain wire connecting part 55d. The plate-shaped part 55c projects to the rear surface side (Y2 side) of the block body 52. The drain wire connecting part 55d includes three lugs 55d1, 55d2, and 55d3. The lugs 55d1, 55d2, and 55d3 are alternately bent in the X1 direction and the X2 direction to have a U-shaped configuration seen from the Y2 side.
A spacer 60 is provided at the rear surface side (Y2 side) of the block body 52 to determine positions of the first wire connecting part 53c, the second wire connecting part 54c and the plate-shaped part 55c. The spacer 60 includes a first groove part 61, a second groove part 62, and a slit 63. The first groove part 61 corresponds to the first signal wire connecting part 53c. The second groove part 62 corresponds to the second signal wire connecting part 54c. The slit 63 corresponds to the plate-shaped part 55c. 
As discussed above, the first signal wire connecting part 53c and the second signal wire connecting part 54c have L-shaped cross-sectional configurations. Therefore, each of the signal wires 23-1 and 23-2 are soldered so that the signal wires 23-1 and 23-2 are positioned at corner parts at insides of the first wire connecting part 53c and the second wire connecting part 54c, respectively.
In addition, the drain wire connecting part 55d has a U-shaped configuration. Therefore, the drain wire 25 is positioned by and soldered to the drain wire connecting part 55d. 
With this structure, it is possible to directly connect the first signal wire 23-1 and the second signal wire 23-2 to the first signal contact 53 and the second signal contact 54 without using a relay board. Hence, it is possible to reduce cross-talk.
FIG. 5 is an exploded perspective view of an inner cap 400 and a shield assembly body 80. FIG. 6 is a view illustrating a gap between the inner cap 400 and the shield assembly body 80 that is closed. In FIG. 6, part (A) is a view seen from the Y2 side. Part (B) of FIG. 6 is a cross-sectional view taken along a line B-B of part (A). Part (C) of FIG. 6 is a cross-sectional view taken along a line C-C of part (A).
The shield assembly body 80 is formed by arranging a first shield cover 81 situated at a Z1 side and a second shield cover 90 situated at a Z2 side. The shield assembly body 80 surrounds the contact assembly body 51, the pair of the lock arms 56 and 57, and the spacer 60.
As illustrated in FIG. 2, the inner cap 400 is provided at the Y2 side of the inside of the shield assembly body 80. Under this structure, when the hood 100 and the outer cover 110 are outsert molded at the shield assembly body 80, it is possible to prevent resin from flowing from a space at the Y2 side of the shield assembly body 80 to the inside.
The inner cap 400 is formed by arranging a first inner cap half 401 at the Z1 side and a second inner cap half 410 at the Z2 side.
The first inner cap half 401 includes a base board part 402 situated at the Z1 side, a pair of engaging parts 403 and 404 situated at the X1 side and the X2 side, respectively, and a back board part 405 situated at the Y2 side.
The engaging parts 403 and 404 include ribs 403c, 403d, 404c, and 404d situated at external surfaces of the engaging parts 403 and 404. The ribs 403c and 403d and the ribs 404c and 404d extend in the Z1-Z2 direction in a line manner over the full height. The ribs 403c and 404c come in contact with an internal surface of the second shield cover 90 with a pressure (force). The ribs 403d and 404d come in contact with an internal surface of the first shield cover 81 with a force.
The back board 405 includes a window part 405b having a substantially semicircular-shaped configuration. The balanced transmission cable 20 is inserted into the window part 405b. 
The second inner cap half 410 includes a base board part 411 and a pair of facing parts 412 and 413.
External surfaces of the pair of facing parts 412 and 413 face corresponding internal surfaces of the pair of the engaging parts 403 and 404 with separation. In spaces 421 and 422 between the external surfaces of the facing parts 412 and 413 and the internal surfaces of the engaging parts 403 and 404, Y2 side ends of the corresponding lock arms 56 and 57 are received. The balanced transmission cable 20 is inserted into the space 414 between the facing parts 412 and 413.
Thus, the ribs 403c, 403d, 404c, and 404d provided at the external surface of the inner cap 400 are in contact with the internal surface of the shield cover assembly 80 with a force, and thereby the spaces between the X1 side surface and the X2 side surface of the inner cap 400 and the X2 side surface and the X1 side surface of the shield assembly body 80 are closed.
In addition, a window part 97b at the Y2 side of the shield cover assembly 80 is closed by the balanced transmission cable 20 and the back board 405 of the first inner cap half 401.
According to the above-discussed structure, a space at the Y2 side of the shield cover assembly 80 can be closed. Therefore, it is possible to prevent resin from flowing to the inside of the shield cover assembly body 80 when the hood 100 and the outer cover 110 are outsert molded.
Last, an assembling process of the balanced transmission cable connector is discussed with reference to FIG. 7. Here, FIG. 7 is a perspective view illustrating a part of the assembling process of the balanced transmission cable connector illustrated in FIG. 7.
First, the first inner cap half 401 is placed inside the first shield cover 81. Then, while the end of the balanced transmission cable 20 is clamped by the ring part 85, as illustrated in FIG. 7, the contact assembly body 51 connected to the end of the balanced transmission cable 20 is installed inside the first shield cover 81 from the Y2 side in the Y1 direction.
Next, the second inner cap half 410 is combined with the first inner cap half 401 so that the inner cap 400 is assembled. Finally, the second inner cap half 410 is covered with the second shield cover 90 in order to be engaged with the first shield cover 81 and thereby the shield cover assembly 80 is assembled.
However, according to the structure discussed at Japanese Laid Open Patent Application Publication No. 2007-12588, as illustrated in FIG. 4(B), the drain wire connecting part 55d, the first signal wire connecting part 53c, and the second signal wire connecting part 54c are exposed from the spacer 60. Accordingly, at the time of soldering, the drain wire connecting part 55d and the first and second signal wire connecting parts 53c and 54c may be soldered in error. Hence, there is room for improvement of soldering operations.
In addition, as illustrated in FIG. 4(B), there are a lot of air layers around the first and second signal wire connecting parts 53c and 54c. Accordingly, characteristic impedance may be higher than a standard value.
Furthermore, according to the structure discussed at Japanese Laid Open Patent Application Publication No. 2007-12588, a window part 405b of the first inner cap half 401 installed in the first shield cover 81 is smaller than the space between the pair of the lock arms 56 and 57. Therefore, as illustrated in FIG. 7, it is necessary to elastically deform the pair of the lock arms 56 and 57 at the time of operations. Hence, there is room for improvement of assembling operations.